Looking for more info on your Soekris DAM1021 upgrade (TWSAFB-OIDAM

[GstewParticipant]

Andrea,

I have a couple of somewhat modified DAM 1021 DACs and am VERY interested in more info on your Soekris DAM1021 upgrade. I have considered additional mods, but am clear the stock clock and clocking scheme limits the performance and am hoping your upgrade boards are the next step I seek.

Some questions…

First, can you outline the general configuration and architecture?

For example, to what board is the I2S input signal fed?

From/To what does each board receive/send it’s input/output?

Related to that, it looks like the TWSADB-OIDAM board is connected via the 18 output connections per channel from the DAM1021 FPGA to the shift registers. Correct? AND is the TWSAFB-OIDAM sending to the DAM1021 or receiving from the DAM1021?

Is the digital filtering implemented in the FPGA still active and used with your upgrade boards?

Also how do you manage dealing with the adaptive clocking scheme in the stock DAM DAC?

Finally, how does little LDO regulator board pictured over the stock DAM1021 regulator and clock fit into all of this?

I know this is a work-in-process, but knowing a little more will help me decide whether to include 1 or 2 of these setups on my GB order.

THANKS!

Greg in Mississippi

[The Well AudioParticipant]

Unfortunately we have not yet found the time to test the DAM1021 upgrade, that’s the reason why we have not yet published the User Manual.

Configuration and architecture are very simple: we only save the switches/ladder part of the DAC, throwing out all the FPGA/micro/PLL section.
This way the saved part of the DAC will be driven directly by the FIFO Lite with its external oscillators.
Therefore I2S input signal will feed the FIFO Lite and no longer the DAM input.

Then the TWSADB-OIDAM board is connected via the 20 output connections per channel from the DAM1021 FPGA to the 595s installed on the DAM DAC (20 instead of 18 because there are also the OE pins of the shift registers).

The digital filtering implemented in the FPGA of the DAM will no longer work because the FPGA part of the DAM will be excluded.
Any upsampling should be done in software before feeding the FIFO Lite which accepts up to 24 bit/384kHz.

Using the FIFO Lite to feed the DAM DAC there is no need to manage the adaptive clocking, no PLL is needed because the FIFO buffer gets the DAC operating in a different time domain, fully isolated from the source.

In order to fit the little LDO regulator board, the onboard regulator has to be removed and replaced with the new board.
There is a switch on the little LDO board wich allows to swith between the stock DAM and the upgraded DAM. Therefore the upgrade is reversible.

[GstewParticipant]

Andrea,

Thanks. This helps a lot.

I guess your answer also suggests you may not be able to answer the question “How does it sound modified compared to other NOS RTR DACs such as the other ones you sell such as your TDA1541A, AD1862, & AD5791, and also your PCM1704?”

Or did you do sufficient prototyping before now to have a feel for how might compare and be ranked?

Just trying to get sufficient info to decide whether continuing to upgrade my Soekris setups is worthwhile or if I should start afresh on a different path.

Also was hoping the stock filtering was retained, I am not a real fan of NOS DACs from what I’ve heard from DACs setup this way in my systems. I understand why you did what you did as keeping the filtering in the FPGA while bypassing the adaptive clocking was likely impossible, but I’d hoped you’d overcome that. OTOH, my end-game is to use these with offline upsampling which would include filtering, so this is still a possible path for me.

Thanks for responses to the above… and for all you are doing!

Greg in Mississippi

[GstewParticipant]

Andrea,

Also 2 questions on the TWSAFB-LT…

First, the documentation says it can be configured ‘one time by USB connection’. Does this mean I can only configure it once and cannot do so again? Or is this just another way of saying I cannot use the USB connection to configure it on-the-fly, though I can take it out of the system and reconfigure it via USB multiple times?

Second, I assume the Optical Isolation for TWSAFB-LT and the Optical Isolation and Reclocker for TWSAFB-LT both perform roughly the same function, but the latter adds reclocking. Why chose one over the other? Any tradeoffs?

THANKS!

Greg in Mississippi

[OlivierParticipant]

gstew,the TWSAFB-LT can be configured in USB as many times as you wish,the TWSAFB-LT  and the TWSAFB-OI /TWSAFB-OIR are complementary.

[Gstew]

Gstew Said

Andrea,

Also 2 questions on the TWSAFB-LT…

First, the documentation says it can be configured ‘one time by USB connection’. Does this mean I can only configure it once and cannot do so again? Or is this just another way of saying I cannot use the USB connection to configure it on-the-fly, though I can take it out of the system and reconfigure it via USB multiple times?

Second, I assume the Optical Isolation for TWSAFB-LT and the Optical Isolation and Reclocker for TWSAFB-LT both perform roughly the same function, but the latter adds reclocking. Why chose one over the other? Any tradeoffs?

THANKS!

Greg in Mississippi

You cannot use the USB connection to configure it on-the-fly, but you can simply connect the USB cable to the FIFO Lite and reconfigure it multiple times.

TWSAFB-LT-OI Optical Isolation simply isolates dirty signals like BCK and DATA from the clean signal LRCK.
It’s recommended for the DACs which switches on LRCK or MCK, like Sabre DAC, TDA1541A, AD1862 and so on.

TWSAFB-LT-OIR Optical Isolation and Reclocker too isolates the dirty signals, but all signals are reclocked by the master clock to decrease the jitter coming from the FPGA of the FIFO.
It’s recommended for the DACs which switches on BCK, like PCM1704, PCM63, PCM1794 and so on.

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